The inadequate treatment of municipal solid waste which is being put in landfills and the increasing addition of nondegradable materials, including plastics, to the municipal solid waste streams are combining to reduce drastically the number of landfills available and to increase the costs of municipal solid waste disposal. While the recycling of reusable components of the waste stream is desirable in many instances, there are some products which do not readily fit into this framework, e.g. disposable personal absorbents such as diapers and sanitary napkins, garbage bags, and numerous other products. The composting of non-recyclable solid waste is a recognized and growing method of reducing solid waste volume for landfilling and/or making a useful product from the waste to improve the fertility of fields and gardens. One of the limitations to marketing such compost is the visible contamination by undegraded plastic such as film and fiber fragments.
As related in the aforesaid parent applications, which are hereby specifically incorporated herein by reference, there was a desire to achieve several objectives, as follows:
1- to provide components which are useful in disposable products and which are degraded into less contaminating forms under the conditions typically existing in waste composting processes. These conditions may involve temperatures no higher than 70 C., and averaging more nearly 55-60 C., humid conditions as high as 100% relative humidity, and exposure times which range from two weeks to more than three months.
2-to provide disposable components which will not only degrade aerobically/anaerobically in composting, but will continue to degrade in the soil or landfill. As long as water is present, they will continue to break down into low molecular weight fragments which can be ultimately biodegraded by microorganisms completely into biogas, biomass and liquid leachate, as for natural organics like wood.
3-to provide novel polyesters for making the aforementioned fibers, films, coatings and nonwoven sheets of the polyesters, and disposable diapers containing the nonwoven sheets.
4-to provide polyesters and derivative products which have low ingredient costs and yet provide strength and toughness properties adequate for end uses such as in disposable diapers.
Accordingly, U.S. Pat. No. 5,053,482 provided useful novel polyesters consisting essentially of recurring structural units of the formula EQU --C(O)--R--C(O)--OGO--
wherein R is about 97.5 to 99.9 mole % para-phenylene (abbreviation T) and about 0.1 to 2.5 mole % of an alkali metal or alkaline earth metal 5-sulfoisophthalate radical (abbreviation 5SI) and wherein G is about 60 to 80 mole % --CH.sub.2 --CH.sub.2 -- (abbreviation 2G) and about 20 to 40 mole % --(CH.sub.2).sub.2 --O--(CH.sub.2).sub.2 -- (abbreviation DEG), and fibers, non-woven sheet, films and combinations thereof, and disposable diapers comprising such materials. The above-mentioned U.S. Pat. Nos. 5,097,004 and 5,092,008 provided other polyesters containing 5SI radicals. U.S. Pat. Nos. 5,171,308 (QP-4691-A), 5,171,309 (DP-4955-A) and 5,219,646 (QP-4850-A), however, disclose useful compostable products are provided from additional polyesters containing sulfonate radicals other than 5SI, for example 4SP, referred to therein and hereinafter. So the object of the present invention is to provide compostable products from such copolyesters derived from 4SP.
Abbreviations and nomenclature herein, except as otherwise indicated, are as described in aforesaid U.S. Pat. No. 5,053,482, and application Ser. Nos. 07/645,849, 07/645,995, 07/769,414, 07/769,417, and 07/771,019, all of which are hereby incorporated herein by reference, as are applications QP-4560-A, QP-4690-A, QP-4691-A, QP-4710-A, QP-4850-A and DP-4955-A, being filed at the present time.